This invention relates generally to the determination of electrical parameters of large samples in situ and more specifically, to the method and means for utilizing the parameters to show the presence of inhomogeniety and anisotropy in large samples.
As an example of one aspect of the invention a "large sample" could be considered a sample of rock and soil in situ. Rock and soil testing under laboratory conditions has been developed to a very satisfactory status. When experimental investigations of large samples in the field are considered, however, varying results occur, the in situ measurements of parameters are not satisfactory and do not match laboratory measurements.
One factor in this discrepancy is the magnitudinous difference in size between samples. In large volumes, many irregularities are encountered, such as cracks, joints voids, weak regions, voids etc. which have a strong influence on the electrical properties of the medium but which are likewise ignored in the testing process for laboratory samples.
Existing methods available for obtaining small signal parameter values for large volumes in situ include geoelectric and seismic measurements. Seismic measurements, coupled with density information, give the average elastic constants of the material. Geoelectric measurements provide information which may be used in a diagnostic sense and under certain circumstances may yield quantities related to the mechanical parameters of the material.
There has thus far been no effective means to provide a direct correlation between the various properties of large volume samples. This invention provides a solution to this problem of the prior art.